Motor for Drawing Well Water

dEAR,

You may have to go for submersible pumps motor set. This does not require earthing to motor. You may go up to any hp rating.

Well, that's one of the alternative but I want to purchase a motor rather than a submersible pump because I want to use it for some other purpose also.

Also we've been using a 100w, 1 phase motor for some other purpose without any earthing, so just wondering why it's unsafe to have a motor of higher capacity without earthing sufficient enough to draw water from well.

No electrical equipment in metal enclosure is safe without earthing.

100W motor being a very fractional hp , may be with plastic enclosure.( like mixer grinder )

You may have to go for very low volt motor - less then 12 Volt one, which I suppose will not suit to lift a water.

Thanx for answering..

But I'm little bit confused regarding the voltage rating you mentioned above.

Being on domestic power supply, its input would be ~ 230v.

By the way, I want to use the same motor for drawing water from well as well as from municipal water tap. So, I don't want to have a submersible pump.

The issue of "not earthing" is only that small appliance type pumps, such as fountain pumps, have the motors encased in non-conductive housings. This is often referred to as being "double insulated" because not only are all the electrical connections insulated inside, but the casing itself is an insulating material.

So with that in mind, the limitation is in what some manufacturer will make as the larges size pump in an insulated housing like that. From a practical standpoint, the value is fairly low because non-conductive means non-metallic, i.e. plastic, and that will begin to distort with heat. That is why for wells, a submersible is a preferable way to go; the water around it allows it to stay cool so you can use a larger power rating. In a non-submersible double-insulated motor design, the largest motor I have ever seen is 825W, a little over 1HP, but that was not for a pump, it was for a tool. For a well pump, assuming you use a jet pump since you don't want to submerge it, you are going to be limited in how much water you can pump within that power limit (assuming you can find a jet pump set up with a double insulated motor). How much you can pump is going to be a function of well depth and required pressure.

I would start by trying to find a double-insulated jet pump.

There are a few points one has to remember with electric motor(water Pump).

As some other postings have rightly pointed out that earthing is indeed essential. And what is most important is, that this is to safeguard user, i.e. yourself from electrical shock hazards, which have turned out at times, fatal. Earthing helps to discharge the leakage current generated due to certain reasons(without getting into technical clits) while an electrical apparatus is in operation. Lack of earthing causes the leakage current to take path through our body (if that is the shrteast path) and when such current passes through our body, we receive an electrical shock. Also, when you have two wires feeding supply to motor, why a third wire for earthing is avoided. I do not understand why many people dodge the "earthing factor", which needs to be emphasized. As other posts have mentioned, with small motors having non-metallic body, the leakage current is also very small and hence earhing may not be necessary, otherwise, it should never be ignored. And need not to mention that there is no "Undo" key available, if you receive electrical shock!!!

After this, when you want to use a motor (non-submersible), you have to consider many factors like depth of water storage, delivery height for water, quantity of water to be transported and the storage capacity of both water tanks(source and destination). These factors decide the motor size and if you visit any water pump dealer, generally they help you out with selection of motor. If it is more than 1 hp, it is definitely not a good idea to swap for your other use. Moreover, for drawing water directly form tap, you may not need water pump of 0.5 hp, if you are not staying above first floor.

Hope this helps you to decide.

Maybe I'm pointing out the obvious or I just misunderstand the reference to "drawing" water from a well. To me it implies that you are attempting to "pull" water to the surface. The major point of well pumps being submersible is to put the pump at the source so it can push the water to the surface, allowing the pump to do the work. Pulling the water only works for a short distance which varies slightly with altitude (and pump design) due to the fact that in this case its dependent on atmospheric pressure to get the water to the pump.

If the equipment is double-insulated and rated at IP68, then no earthing is required.

I believe one reason for metal cases on larger motors is to complete the magnetic circuit more effectively.

The other reason of course is strength and damage tolerance.

Motors often get a hard time.

Are you wanting to put your motor on something like a windmill pump? (ie positive displacement with the working part down near water level). In that case it may well be feasible to swap the motor to other uses.

If you are working on a suction lift, and are near sea level, you will be limited to max of about 7m lift (theoretical is near 10m, but factors in the pump reduce this).

A jet pump uses a flow of water through a venturi. The pressure drop at the throat is used to suck more water in and the combined flow is pushed to the surface. While not very efficient, the venturi is small and can be dropped down a small bore hole. meanwhile, the mechanical and electrical parts stay on the surface. This arrangement could well allow you to swap the motor from one duty to another.

I don't quite understand why you need to put a pump on the mains water supply. have you very low pressure? or do you need significantly higher than normal pressure?